Police were hunting a lone gunman on the loose in central Paris today after he opened fire at the offices of a left-wing newspaper and a major bank before hijacking a car to take him to the Champs-Élysées.

The shaven-haired assailant, who police said was filmed by video-surveillance cameras, fired shots at the office of Libération daily, seriously injuring a photographer’s assistant before fleeing, police and staff at the newspaper said.

About 90 minutes later, he opened fire outside the suburban headquarters of Sociéte Generale in the La Défense business district 10 km west of the centre, wounding no one, police and a spokeswoman for the bank said.

There was no immediate indication of his motive.

Shortly afterwards, the same man hijacked a car nearby and forced the driver to drop him on the Avenue de Champs-Élysées in central Paris, the driver told police.

Police said the description of the car-jacker fitted that of the gunman, who was armed with a hunting rifle or similar weapon. Cartridges found after both attacks corresponded.

“As long as this person is still on the loose and we do not know the motives, this represents a threat,” Interior Minister Manuel Valls told reporters outside Libération’s offices. “We must move fast.”

A police helicopter hovered over the Champs-Élysées area to help in the manhunt after the gunman melted into the crowd.

President Francois Hollande, on an official visit to Israel and the Palestinian territories, said “all means” would be deployed to catch the attacker.

Earlier, Libération managing editor Fabrice Rousselot said witnesses described the assailant as a short-haired man in his 40s.

Police said he was “of European type”. The wounded photographer’s assistant was hit in the chest, a police official said. “He walked in, fired twice and left,” Mr Rousselot told reporters.

Deputy editor-in-chief Fabrice Tassel said in a tweet that the young male victim was fighting for his life in hospital.

Police deployed outside the offices of other media outlets in the French capital.

The mid-morning incidents came days after an armed intruder entered the offices of the BFM TV channel, threatening journalists before disappearing. Police said video surveillance footage showed it was the same man. Liberation’s offices near the Place de la Republique in east-central Paris were cordoned off as forensics experts investigated.